Tag: SOFIA

Astronomers are understandanly fascinated with the Epsilon Eridani system. For one, this star system is in close proximity to our own, at a distance of about 10.5 light years from the Solar System. Second, it has been known for some time that it contains two asteroid belts and a large debris disk. And third, astronomers have suspected for many years that this star may also have a system of planets.

On top of all that, a new study by a team of astronomers has indicated that Epsilon Eridani may be what our own Solar System was like during its younger days. Relying on NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft, the team conducted a detailed analysis of the system that showed how it has an architecture remarkably similar to what astronomer believe the Solar System once looked like.

Led by Kate Su – an Associate Astronomer with the Steward Observatory at the University of Arizona – the team includes researchers and astronomers from the Department of Physics & Astronomy of Iowa State University, the Astrophysical Institute and University Observatory at the University of Jena (Germany), and NASA’s Jet Propulsion Laboratory and Ames Research Center.

Artist’s diagram showing the similar structure of the Epsilon Eridani to the Solar System. Credit: NASA/JPL-Caltech

For the sake of their study – the results of which were published in The Astronomical Journal under the title “The Inner 25 AU Debris Distribution in the Epsilon Eri System” – the team relied on data obtained by a flight of SOFIA in January 2015. Combined with detailed computer modeling and research that went on for years, they were able to make new determinations about the structure of the debris disk.

As already noted, previous studies of Epsilon Eridani indicated that the system is surrounded by rings made up of materials that are basically leftovers from the process of planetary formation. Such rings consist of gas and dust, and are believed to contain many small rocky and icy bodies as well – like the Solar System’s own Kuiper Belt, which orbits our Sun beyond Neptune.

Careful measurements of the disk’s motion has also indicated that a planet with nearly the same mass as Jupiter circles the star at a distance comparable to Jupiter’s distance from the Sun. However, based on prior data obtained by the NASA’s Spitzer Space Telescope, scientists were unable to determine the position of warm material within the disk – i.e. the dust and gas – which gave rise to two models.

In one, warm material is concentrated into two narrow rings of debris that orbit the star at distances corresponding respectively to the Main Asteroid Belt and Uranus in our Solar System. According to this model, the largest planet in the system would likely be associated with an adjacent debris belt. In the other, warm material is in a broad disk, is not concentrated into asteroid belt-like rings, and is not associated with any planets in the inner region.

Using the new SOFIA images, Su and her team were able to determine that the warm material around Epsilon Eridani is arranged like the first model suggests. In essence, it is in at least one narrow belt, rather than in a broad continuous disk. As Su explained in a NASA press release:

“The high spatial resolution of SOFIA combined with the unique wavelength coverage and impressive dynamic range of the FORCAST camera allowed us to resolve the warm emission around eps Eri, confirming the model that located the warm material near the Jovian planet’s orbit. Furthermore, a planetary mass object is needed to stop the sheet of dust from the outer zone, similar to Neptune’s role in our solar system. It really is impressive how eps Eri, a much younger version of our solar system, is put together like ours.”

These observations were made possible thanks to SOFIA’s on-board telescopes, which have a greater diameter than Spitzer – 2.5 meters (100 inches) compared to Spitzer’s 0.85 m (33.5 inches). This allowed for far greater resolution, which the team used to discern details within the Epsilon Eridani system that were three times smaller than what had been observed using the Spitzer data.

In addition, the team made use of SOFIA’s powerful mid-infrared camera – the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST). This instrument allowed the team to study the strongest infrared emissions coming from the warm material around the star which are otherwise undetectable by ground-based observatories – at wavelengths between 25-40 microns.

This artist’s conception of the Epsilon Eridani system, the closest star system who’s structure resembles a young Solar System. Credit: NASA/JPL/Caltech

These observations further indicate that the Epsilon Eridani system is much like our own, albeit in younger form. In addition to having asteroid belts and a debris disk that is similar to our Main Belt and Kuiper Belt, it appears that it likely has more planets waiting to be found within the spaces between. As such, the study of this system could help astronomers to learn things about the history of our own Solar System.

Massimo Marengo, one of he co-authors of the study, is an Associate Professor with the Department of Physics & Astronomy at Iowa State University. As he explained in a University of Iowa press release:

“This star hosts a planetary system currently undergoing the same cataclysmic processes that happened to the solar system in its youth, at the time in which the moon gained most of its craters, Earth acquired the water in its oceans, and the conditions favorable for life on our planet were set.”

At the moment, more studies will need to be conducted on this neighboring stars system in order to learn more about its structure and confirm the existence of more planets. And it is expected that the deployment of next-generation instruments – like the James Webb Space Telescope, scheduled for launch in October of 2018 – will be extremely helpful in that regard.

“The prize at the end of this road is to understand the true structure of Epsilon Eridani’s out-of-this-world disk, and its interactions with the cohort of planets likely inhabiting its system,” Marengo wrote in a newsletter about the project. “SOFIA, by its unique ability of capturing infrared light in the dry stratospheric sky, is the closest we have to a time machine, revealing a glimpse of Earth’s ancient past by observing the present of a nearby young sun.”

Ever burnt meat or grilled chicken till the skin was crisp? If you have, you’ve made some PAHs. Overcooked meats, burning wood and automobile exhaust release PAHs, complex molecules composed of carbon (shown here at “C”) and hydrogen (“H”). This ball-and-stick figure represents benzo[a]pyrene, a PAH commonly produced when cooking food or burning wood has 20 carbon atoms and a dozen hydrogens. Credit: Dennis Bogdan with additions by the authorKitchens are where we create. From crumb cake to corn on the cob, it happens here. If you’re like me, you’ve occasionally left a turkey too long in the oven or charred the grilled chicken. When meat gets burned, among the smells informing your nose of the bad news are flat molecules consisting of carbon atoms arranged in a honeycomb pattern called PAHs or polycyclic aromatic hydrocarbons.

PAHs make up about 10% of the carbon in the universe and are not only found in your kitchen but also in outer space, where they were discovered in 1998. Even comets and meteorites contain PAHs. From the illustration, you can see they’re made up of several to many interconnected rings of carbon atoms arranged in different ways to make different compounds. The more rings, the more complex the molecule, but the underlying pattern is the same for all.

Both simple and complex organic (carbon-containing) molecules have been found in space. Carbon is formed in the cores of red giant stars, where it gets cycled to the surface and dispensed into space. Credit: IAC; original image of the Helix Nebula (NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner, STScI, & T.A. Rector, NRAO

All life on Earth is based on carbon. A quick look at the human body reveals that 18.5% of it is made of that element alone. Why is carbon so crucial? Because it’s able to bond to itself and a host of other atoms in a variety of ways to create a lots of complex molecules that allow living organisms to perform many functions. Carbon-rich PAHs may even have been involved in the evolution of life since they come in many forms with potentially many functions. One of those may have been to encourage the formation of RNA (partner to the “life molecule” DNA).

In the continuing quest to learn how simple carbon molecules evolve into more complex ones and what role those compounds might play in the origin of life, an international team of researchers have focused NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) and other observatories on PAHs found within the colorful Iris Nebula in the northern constellation Cepheus the King.

This photo is a combination of three infrared color images of the Iris Nebula (NGC 7023) from SOFIA (red & green) and Spitzer (blue) that shows different types of PAH molecules in different parts of the nebula. Credits: NASA/DLR/SOFIA/B. Croiset, Leiden Observatory, and O. Berné, CNRS; NASA/JPL-Caltech/Spitzer

Bavo Croiset of Leiden University in the Netherlands and team determined that when PAHs in the nebula are hit by ultraviolet radiation from its central star, they evolve into larger, more complex molecules. Scientists hypothesize that the growth of complex organic molecules like PAHs is one of the steps leading to the emergence of life.

Strong UV light from a newborn massive star like the one that sets the Iris Nebula aglow would tend to break down large organic molecules into smaller ones, rather than build them up, according to the current view. To test this idea, researchers wanted to estimate the size of the molecules at various locations relative to the central star.

The research team used a telescope on board NASA’s SOFIA Observatory, a modified Boeing 747, to fly high above most of the water vapor in the atmosphere to get a better view of PAHs in the Iris Nebula in infrared light. Credit: NASA

Croiset’s team used SOFIA to get above most of the water vapor in the atmosphere so he could observe the nebula in infrared light, a form of light invisible to our eyes that we detect as heat. SOFIA’s instruments are sensitive to two infrared wavelengths that are produced by these particular molecules, which can be used to estimate their size. The team analyzed the SOFIA images in combination with data previously obtained by the Spitzer infrared space observatory, the Hubble Space Telescope and the Canada-France-Hawaii Telescope on the Big Island of Hawaii.

The analysis indicates that the size of the PAH molecules in this nebula vary by location in a clear pattern. The average size of the molecules in the nebula’s central cavity surrounding the young star is larger than on the surface of the cloud at the outer edge of the cavity. They also got a surprise: radiation from the star resulted in net growth in the number of complex PAHs rather than their destruction into smaller pieces.

A view of the Iris Nebula in normal or visible light showing the bright, young central star. Light from the star illuminates clouds of gas and dust that show the nebula’s flower-like shape. Credit: Hunter Wilson

In a paper published in Astronomy and Astrophysics, the team concluded that this molecular size variation is due both to some of the smallest molecules being destroyed by the harsh ultraviolet radiation field of the star, and to medium-sized molecules being irradiated so they combine into larger molecules.

So much starts with stars. Not only do they create the carbon atoms at the foundation of biology, but it would appear they shepherd them into more complex forms, too. Truly, we can thank our lucky stars!

“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars,” Carl Sagan famously said in his 1980 series Cosmos. “We are made of starstuff.”

And even today, observations with NASA’s airborne SOFIA observatory are supporting this statement. Measurements taken of the dusty leftovers from an ancient supernova located near the center our galaxy – aka SNR Sagittarius A East – show enough “starstuff” to build our entire planet many thousands of times over.

“Our observations reveal a particular cloud produced by a supernova explosion 10,000 years ago contains enough dust to make 7,000 Earths,” said research leader Ryan Lau of Cornell University in Ithaca, New York – the same school, by the way, where Carl Sagan taught astronomy and space science.

Composite image of SNR Sgr A East showing infrared SOFIA data outlined in white against X-ray and radio observations. (NASA/CXO/Herschel/VLA/Lau et al.)

While it’s long been known that supernovae expel enormous amounts of stellar material into space, it wasn’t understood if clouds of large-scale dust could withstand the immense shockwave forces of the explosion.

These observations, made with the joint NASA/DLR-developed Faint Object InfraRed Camera for the SOFIA Telescope (FORCAST) instrument, provide key “missing-link” evidence that dust clouds do in fact survive intact, spreading outward into interstellar space to seed the formation of new systems.

Interstellar dust plays a vital role in the evolution of galaxies and the formation of new stars and protoplanetary discs – the orbiting “pancakes” of material around stars from which planets (and eventually everything on them) form.

The findings may also answer the question of why young galaxies observed in the distant universe possess so much dust; it’s likely the result of frequent supernova explosions from massive early-generation stars.

Dreams of space are often tied to jet engines or solar sails or taking a ride on a rocketship. But it’s often quite efficient to do research from Earth, especially from the high reaches of the atmosphere where there are few molecules to get in the way of observations.

NASA wants to do more of this kind of astronomy with an airship — but at an extreme height of 65,000 feet (20 kilometers) for 20 hours. No powered-airship mission has managed to last past eight hours at this height because of the winds in that zone, but NASA is hoping that potential creators would be up to the challenge.

This isn’t a guaranteed mission yet. NASA has a solicitation out right now to gauge interest from the community, and to figure out if it is technically feasible. This program would be a follow-on to ideas such as SOFIA, a flying stratospheric telescope that the agency plans to defund in future budgets.

Their goal is to fly an airship with a 44-pound (20-kilogram) payload at this altitude for 20 hours. If a company is feeling especially able, it can even try for a more difficult goal: a 440-pound (200-kilogram) payload for 200 hours.

“We are seeking to take astronomy and Earth science to new heights by enabling a long-duration, suborbital platform for these kinds of research,” stated lead researcher Jason Rhodes, an astrophysicist at NASA’s Jet Propulsion Laboratory in California.

And why not just use a balloon? It comes down to communications, NASA says: “Unlike a balloon, which travels with air currents, airships can stay in one spot,” the agency states. “The stationary nature of airships allows them to have better downlink capabilities, because there is always a line-of-sight communication.”

Just weeks after becoming fully operational, the Stratospheric Observatory for Infrared Astronomy (SOFIA) is facing storage in 2015. The airborne observatory costs NASA about $85 million annually, making it one of the more expensive missions the agency has. Yesterday, administrator Charlie Bolden told reporters that it was a matter of making choices, and that the money from SOFIA could go to missions such as Cassini.

Much of the expense comes from flying the modified 747 airplane to carry the telescope, which was built by the Germans and has a mirror of about 2.5 meters (100 inches). NASA said it is possible that DLR could take on more of the cost, and said it is in discussions with the German space agency to figure out the telescope’s future.

The telescope saw its first light in 2010. Here are some of the special things it’s spotted in three years and about 400 hours of flying.

Mighty Jupiter’s heat

Infrared image of Jupiter from SOFIA’s First Light flight composed of individual images at wavelengths of 5.4 (blue), 24 (green) and 37 microns (red) made by Cornell University’s FORCAST camera. A recent visual-wavelength picture of approximately the same side of Jupiter is shown for comparison. The white stripe in the infrared image is a region of relatively transparent clouds through which the warm interior of Jupiter can be seen. (Visual image credit: Anthony Wesley)

This is one of the first observations that SOFIA performed. “The crowning accomplishment of the night came when scientists on board SOFIA recorded images of Jupiter,” said USRA SOFIA senior science advisor Eric Becklin in 2010. “The composite image from SOFIA shows heat, trapped since the formation of the planet, pouring out of Jupiter’s interior through holes in its clouds.”

M82 supernova

Image of M82 including the supernova at near-infrared wavelengths J, H, and K (1.2, 1.65, and 2.2 microns), made Feb. 20 by the FLITECAM instrument on SOFIA. (NASA/SOFIA/FLITECAM team/S. Shenoy)

Although a lot of observatories are checking out the recent star explosion, SOFIA’s observations found heavy metals being thrown out in the supernova. “When a Type Ia supernova explodes, the densest, hottest region within the core produces nickel 56,” said Howie Marion from the University of Texas at Austin, a co-investigator aboard the flight, a few days ago. “The radioactive decay of nickel-56 through cobalt-56 to iron-56 produces the light we are observing tonight. At this life phase of the supernova, about one month after we first saw the explosion, the H- and K-band spectra are dominated by lines of ionized cobalt. We plan to study the spectral features produced by these lines over a period of time and see how they change relative to each other. That will help us define the mass of the radioactive core of the supernova.”

A star nursery

This mid-infrared image of the W40 star-forming region of the Milky Way galaxy was captured recently by the FORCAST instrument on the 100-inch telescope aboard the SOFIA flying observatory. (NASA / FORCAST image)

In 2011, SOFIA turned its eyes to star-forming region W40 and was able to peer through the dust to see some interesting things. The telescope was able to look at the bright nebula in the center, which includes six huge stars that are six to 20 times more massive than the sun.

These three pictures demonstrate how one famous star-forming region — in the Orion nebula — appears different in three different telescopes. As NASA wrote in 2011, “SOFIA’s observations reveal distinctly different aspects of the M42 star formation complex than the other images. For example, the dense dust cloud at upper left is completely opaque in the visible-light image, partly transparent in the near-infrared image, and is seen shining with its own heat radiation in the SOFIA mid-infrared image. The hot stars of the Trapezium cluster are seen just above the centers of the visible-light and near-infrared images, but they are almost undetectable in the SOFIA image. At upper right, the dust-embedded cluster of high-luminosity stars that is the most prominent feature in the SOFIA mid-infrared image is less apparent in the near-infrared image and is completely hidden in the visible-light image.”

NASA is prepared to axe an airborne telescope to keep “higher-priority” programs such as the Saturn Cassini mission going, according to budget documents the agency released today (March 4). We have more information about the budget below the jump, including the rationale for why NASA is looking to shelve its Stratospheric Observatory for Infrared Astronomy (SOFIA).

NASA’s has been flying the telescope for just over three years and recently took some nice snapsnots of the M82 supernova that astronomers have been eager to image. The agency’s administrator, however, said SOFIA has had its shot and it’s time to reallocate the money for other programs.

“SOFIA has earned its way, and it has done very well, but we had to make a choice,” said NASA administrator Charlie Bolden in a conference call with reporters regarding the fiscal 2015 $17.46 billion budget request. He added that NASA is in discussions with partner DLR (the German space agency) to look at alternatives, but pending an agreement, the agency will shelve the telescope in 2015.

In a short news conference focusing on the telescope only, NASA said the observatory had been slated to run for another 20 years, at a cost of about $85 million on NASA’s end per year. (That adds up to $1.7 billion in that timeframe by straight math, but bear in mind the detailed budget estimates are not up yet, making that figure a guess on Universe Today’s part.) DLR funds about 25% of the telescope’s operating budget, and NASA the rest.

“SOFIA does have a rather large operating cost compared to other missions, second only to Hubble [Space Telescope],” said NASA chief financial officer Beth Robinson in the second conference call. “There is a distinct trade in the operating mission universe about how many keep going and how much you free up (for new missions).”

SOFIA examines a “unique” part of the infrared spectrum, added NASA’s Paul Hertz, who heads the astrophysics division, but he noted infrared science is also performed by the Spitzer Space Telescope and the European Southern Observatory’s Atacama Large Millimeter Array. Coming up soon is the James Webb Space Telescope. Also, the budget allocates development money for a new infrared observatory called Wide-Field Infrared Survey Telescope (WFIRST).

Below are other notable parts of the 2015 budget. These are high-level statements missing some detail, as the rest of NASA’s documentation won’t be released publicly until late this week or early next.

The full mosaic from the Cassini imaging team of Saturn on July 19, 2013… the “Day the Earth Smiled”

– NASA’s budget falls overall to $17.46 billion, down one percent from $17.64 billion. Planetary science and human exploration each had nearly equal reductions of around three percent, with education taking the deepest cut (24%) in high-level categories as NASA moves to consolidate that directorate with other agencies.

– NASA plans a mission to Europa. This was identified as the “second highest priority Flagship mission for the decade” in the National Research Council planetary science decadal survey, which called for a mission for “characterization of Europa’s ocean and interior, ice shell, chemistry and composition, and the geology of prospective landing sites.” NASA has allocated $15 million in fiscal 2015 for this mission, but it’s unclear if it’s going to be a big mission or a small one as the agency is still talking with the science community (and presumably checking its budget, although officials didn’t say that). If this goes through, it would fly in the 2020s.

– NASA’s humans-to-asteroid mission gets some more money. The agency requests $133 million for goals including “advancing solar electric propulsion and capture systems, and conduct of the Mission Concept Review in which the mission architecture will be established.” During the conference call with reporters, Bolden said the asteroid capture mission is a key step for NASA’s aim to have a manned Mars mission in the 2030s.

– Funding continues for NASA’s commercial crew program and Orion/Space Launch System program. It remains to be seen if the amounts allocated will be enough for what industry insiders hope for, but on a numbers basis, the Orion/SLS infrastructure funding falls to $2.78 billion (down 12% from $3.115 billion in FY 2014) and commercial crew funding increases to $848.3 million (up 20% from $696 million in FY 2014). Note the 2014 numbers are not finalized yet. NASA says the commercial funding will allow the program to maintain “competition”, although details are under wraps as the agency is evaluating proposals.

– The International Space Station is extended to 2024. That news was made public in early January, but technically speaking that is a part of the fiscal 2015 budget.

There’s far more to the budget that could be covered in a single news article, and it should be noted there was an entire aviation component as well. We encourage you to check out the budget documents below for the full story so far.

After 16 days off the job, most employees at NASA returned to work today (Oct. 17). The good news came after a late-night deal by U.S. politicians to reopen government activities until Jan. 15 and raise the debt limit — originally expected to expire today — until Feb. 7. Democrats and Republicans were battling over the implementation of a new health care law; more details on how the deal was reached are available in this New York Times article.

During the shutdown, only mission-essential functions at NASA were completed except at areas such as the Jet Propulsion Laboratory, which are run by contractors. Twitter, Facebook and social media updates went silent. Missions were run on a needs-only basis, and for a while it looked as though the upcoming MAVEN mission to Mars might be delayed (although it got an exception due to its role as a communications relay for NASA’s rovers.)

So you can imagine the happiness on social media when NASA employees returned to work.

Given the length of the shutdown, not all work can just start immediately. Experiments have been left unattended for more than two weeks. Equipment needs to be powered back on. Cancelled meetings and travel arrangements need to, as it is possible, be rebooked.

At NASA’s Marshall Space Flight Center, spokesperson Don Amatore asked employees to be mindful of safety precautions, according to All Alabama. He also stated that “liberal leave” is in effect for employees today and on Friday, meaning that employees are able to take time off without requesting it beforehand — as long as their supervisors know.

Several Twitter reports from NASA contractors on Thursday also indicated that they were unsure if they would be coming back to work on that day, or at some point in the near future. The agency, however, was reportedly sending automated telephone updates to employees and contractors advising them to check with their supervisors for information.

The Stratospheric Observatory for Infrared Astronomy, or SOFIA, 747SP basks in the light of a full moon shining over California’s Mojave Desert. Photo / Tom Tschida

The long-term effects of the shutdown are still coming to light. Certain NASA researchers who planned Antarctic work this year may lose their entire field season. Also, some researchers using NASA or government telescopes missed their “window” of telescope time. “SOFIA remains grounded as a testament to stupidity. Europa keeps her secrets,” wrote Mike Brown, a professor of planetary astronomy at the California Institute of Technology, on Twitter Oct. 13 about NASA’s Stratospheric Observatory for Infrared Astronomy.

Additionally, the S&P ratings agency noted that the U.S. economy lost $24 billion due to the shutdown, which is more than the initial $17.7 billion request for NASA’s budget in fiscal 2014. Given the agency is in the midst of budget negotiations and is worried about the viability of the commercial crew program, among other items, any long-term economic damage could hurt NASA for a while.

NASA and other government agencies also have only three months of relative stability until the government reaches another funding deadline. What do you think will happen next? Let us know in the comments.

One of the most remarkable observatories in the world does its work not on a mountaintop, not in space, but 45,000 feet high on a Boeing 747. Nick Howes took a look around this unique airliner as it made its first landing in Europe.
SOFIA (Stratospheric Observatory for Infrared Astronomy) came from an idea first mooted in the mid-1980s. Imagine, said scientists, using a Boeing 747 to carry a large telescope into the stratosphere where absorption of infrared light by atmospheric water molecules is dramatically reduced, even in comparison with the highest ground-based observatories. By 1996 that idea had taken a step closer to reality when the SOFIA project was formally agreed between NASA (who fund 80 percent of the cost of the 330 million dollar mission, an amount comparable to a single modest space mission) and the German Aerospace Centre (DLR, who fund the other 20 percent). Research and development began in earnest using a highly modified Boeing 747SP named the ‘Clipper Lindburgh’ after the famous American pilot, and where the ‘SP’ stands for ‘Special Performance’.

Maiden test flights were flown in 2007, with SOFIA operating out of NASA’s Dryden Flight Research Center at Edwards Airforce Base in the Rogers Dry Lake in California – a nice, dry location that helps with the instrumentation and aircraft operationally.

This scale model shows the telescope position and how the aircraft design works around it. Credit: Nick Howes.

As the plane paid a visit to the European Space Agency’s astronaut training centre in Cologne, Germany, I was given a rare opportunity to look around this magnificent aircraft as part of a European Space ‘Tweetup’ (a Twitter meeting). What was immediately noticeable was the plane’s shorter length to the ones you usually fly on, which enables the aircraft to stay in the air for longer, a crucial aspect for its most important passenger, the 2.7-metre SOFIA telescope. Its Hubble Space Telescope-sized primary mirror is aluminium coated and bounces light to a 0.4-metre secondary, all in an open cage framework that literally pokes out of the side of the aircraft.

As we have seen, the rationale for placing a multi-tonne telescope on an aircraft is that by doing so it is possible to escape most of the absorption effects of our atmosphere. Observations in infrared are largely impossible for ground-based instruments at or near sea-level and only partially possibly even on high mountaintops. Water vapour in our troposphere (the lower layer of the atmosphere) absorbs so much of the infrared light that traditionally the only way to beat this was to send up a spacecraft. SOFIA can fill a niche by doing nearly the same job but at far less risk and with a far longer life-span. The aircraft has sophisticated infrared monitoring cameras to check its own output,and water vapour monitoring to measure what little absorption is occurring.

The 2.7-metre mirror (although actually only 2.5-metres is really used in practice,) uses a glass ceramic composite that is highly thermally tolerant, which is vital given the harsh conditions that the aircraft puts the isolated telescope through. If one imagines the difficulty amateur astronomers have some nights with telescope stability in blustery conditions, spare a thought for SOFIA, whose huge f/19.9 Cassegrain reflecting telescope has to deal with an open door to the
800 kilometres per hour (500 miles per hour) winds .Nominally some operations will occur at 39,000 feet (approximately 11,880 metres) rather than the possible ceiling of 45,000 feet (13,700 metres), because while the higher altitude provides slightly better conditions in terms of lack of absorption (still above 99 percent of the water vapour that causes most of the problems), the extra fuel needed means that observation times are reduced significantly, making the 39,000
feet altitude operationally better in some instances to collect more data. The aircraft uses a cleverly designed air intake system to funnel and channel the airflow and turbulence away from the open telescope window, and speaking to the pilots and scientists, they all agreed that there was no effect caused by any output from the aircraft engines as well.

Staying cool

The cameras and electronics on all infrared observatories have to be maintained at very low temperatures to avoid thermal noise from them spilling into the image, but SOFIA has an ace up its sleeve. Unlike a space mission (with the exception of the servicing missions to the Hubble Space Telescope that each cost $1.5 billion including the price of launching a space shuttle), SOFIA has the advantage of being able to replace or repair instruments or replenish its coolant, allowing an estimated life-span of at least 20 years, far longer than any space-based infrared mission that runs out of coolant after a few years.

Meanwhile the telescope and its cradle are a feat of engineering. The telescope is pretty much fixed in azimuth, with only a three-degree play to compensate for the aircraft, but it doesn’t need to move in that direction as the aircraft, piloted by some of NASA’s finest, performs that duty for it. It can work between a 20–60 degree altitude range during science operations. It’s all been engineered to tolerances that make the jaw drop. The bearing sphere, for example, is polished to an accuracy of less than ten microns, and the laser gyros provide angular increments of 0.0008 arcseconds. Isolated from the main aircraft by a series of pressurised rubber bumpers, which are altitude compensated, the telescope is almost completely free from the main bulk of the 747, which houses the computers and racks that not only operate the telescope but provide the base station for any observational scientists flying with the plane.

PI in the Sky

The science principle investigators get to sit in relative comfort close to the telescope. Credit: Nick Howes.

The Principle Investigator station is located around the mid-point of the aircraft, several metres from the telescope but enclosed within the plane (exposed to the air at 45,000 feet, the crew and scientists would otherwise be instantly killed). Here, for ten or more hours at a time, scientists can gather data once the door opens and the telescope is pointing at the target of choice, with the pilots following a precise flight path to maintain both the instrument pointing accuracy and also to best avoid the possibility of turbulence. Whilst ground-based telescopes can respond quickly to events such as a new supernova, SOFIA is more regimented in its science operations and, with proposal cycles over six months to a year, one has to plan quite accurately how best to observe an object.

Forecasting the future

Science operations started in 2010 with FORCAST (Faint Object Infrared Camera for Sofia Telescope) and continued into 2011 with the GREAT (German Receiver for Astronomy at Teraherz Frequencies) instrument. FORCAST is a mid/far infrared instrument working with two cameras between at five and forty microns (in tandem they can work between 10–25 microns) with a 3.2 arcminute field-of-view. It saw first light on Jupiter and the galaxy Messier 82, but will be working on imaging the galactic centre, star formation in spiral and active galaxies and also looking at molecular clouds, one of its primary science goals enabling scientists to accurately determine dust temperatures and more detail on the morphology of star forming regions down to less than three-arcsecond resolution (depending on the wavelength the instrument works at). Alongside this, FORCAST is also able to perform grism (i.e. a grating prism) spectroscopy, to get more detailed information on the composition of objects under view. There is no adaptive optics system, but it doesn’t need one for the types of operations it’s doing.

FORCAST and GREAT are just two of the ‘basic’ science operation instruments, which also include Echelle spectrographs, far infrared spectrometers and high resolution wideband cameras, but already the science team are working on new instruments for the next phase of operations. Instrumentation switch over, whilst complex, is relatively quick (comparable to the time it takes to switch instruments on larger ground observatories), and can be achieved in readiness for observations, which the plane aims to do up to 160 times per year. And whilst there were no firm plans to build a sister ship for SOFIA, there have been discussions among scientists to put a larger telescope on an Airbus A380.

A model of the telescope shows its unique control and movement mechanism as well as the optical tube assembly. Credit: Nick Howes.

Sky Outreach

With a planned science ambassador programme involving teachers flying on the aircraft to do research, SOFIA’s public profile is going to grow. The science output and possibilities from instruments that are constantly evolving, serviceable and improvable every time it lands is immeasurable in comparison to space missions. Journalists had only recently been afforded the opportunity to visit this remarkable aircraft, and it was a privilege and honour to be one of the first people to see it up close. To that end I wish to thank ESA and NASA for the invitation and chance to see something so unique.